1. Field of the Invention
The present invention relates to a method of manufacturing chip type electronic parts, more particularly a method of forming terminal electrodes on main bodies of chip type electronic parts.
2. Description of the Related Art
With advancement in packaging techniques, electronic parts such as laminated condensers, laminated coils, LC filters, thin film coils, high frequency antennas, and EMI filters have been quickly improved to have a chip component shape. With the chips becoming more and more compact, it is difficult to form terminal electrodes on the surfaces of the electronic parts with a high degree of precision.
The following process has been used to form terminal electrodes of chip type electronic parts. A thick film paste is applied to the surfaces of the electronic parts using a screen printing method or a transferring method, then, a burning treatment is performed so as to form terminal electrodes on the chip type electronic parts (this will be hereinafter referred to as xe2x80x9cconventional art 1xe2x80x9d). However, when the screen printing or the transferring methods are used to form the terminal electrodes, the paste for the terminal electrodes are likely to be formed into a hemisphere shape on the end face of the chip type electronic part. This frequently causes the chip type electronic part to rise up above the surface to which it is being soldered during the soldering process. Further, since it is necessary to perform the burning treatment, the above method cannot be used to manufacture electronic parts formed from a material such as an electrically insulating organic resin which exhibits a high resistance to heat.
Another conventional method for applying the electrodes uses a metallic mask which is attached to one of the surfaces of the electronic part and applies the terminal electrodes by way of a sputtering method or the like (this will be hereinafter referred to as xe2x80x9cconventional art 2xe2x80x9d). However, in this process, a clearance must be provided between the metal mask and the surface of the electronic parts with the result that sputtering ions get into such clearance, making it difficult to form terminal electrodes having a micro-structure.
In order to overcome the foregoing problems, research has been conducted to develop a method of forming terminal electrodes by way of electroless plating. According to this method, the entire surfaces of the electronic parts are first coated with an active catalyst liquid consisting of tin chloride and palladium chloride and the like. After that, the chip parts are dipped in an electroless plating bath so as to precipitate the plating metal on the entire surfaces of the chip parts. Subsequently, a photoresist layer is formed on the surfaces of the chip type electronic parts and a patterning process is conducted by means of light exposure using a photo-mask, followed by an etching treatment to remove undesired portions of the plating metal, thereby forming the terminal electrodes (this will be hereinafter referred to as xe2x80x9cconventional art 3xe2x80x9d).
According to this method, it is possible to uniformly form terminal electrode layers on the surfaces of the electronic parts without having to perform a burning treatment on the substrates thereof. Further, it avoids the foregoing problem associated with the conventional art 2 (i.e. sputtering ions invade the clearance formed between the metal mask and the surfaces of the electronic parts).
However, the conventional art 3 has the following problems. Since it is necessary to remove portions of the plating metal by means of etching treatment, this method can not be used in manufacturing electronic parts which are made of a material apt to be damaged by this etching treatment.
In addition, with regard to chip type electronic parts of surface mounting type, it is necessary that the terminal electrodes be formed in a U-shaped configuration such that the end portions of the substrates may be surrounded by said terminal electrodes. However, with conventional art 3, when terminal electrodes having the U-shaped configuration are to be formed, it is necessary to repeatedly carry out a process involving the use of photolithography technique and etching removal of the plating metal from the surfaces of chip substrates, on each side of the electronic part making the process complex.
The present invention can solve the aforementioned problems associated with the conventional art and is directed to a method of producing terminal electrodes with the use of a simplified process, which is capable of uniformly and thinly forming terminal electrodes on the surfaces of chip type electronic parts, making it possible to manufacture terminal electrodes having a microstructure, without bringing about any damage to the surfaces of the electronic parts.
The method of manufacturing chip type electronic parts, comprises the steps of: applying a photo-active catalyst liquid to chip substrates to form a photo-sensitive film consisting of the photo-active catalyst liquid on the chip substrates; arranging the chip substrates with respect to a light source in a manner such that portions of the chip substrates on which electrodes are to be formed will become light irradiation portions; irradiating the chip substrates with a light so as to activate irradiated portions of the photo-sensitive film; dipping the chip substrates in an electroless plating bath and precipitating a plating metal on said activated portions.
According to the present invention, it is possible to uniformly and thinly forming terminal electrodes on the surface of chip substrates, making it possible to manufacture terminal electrodes having a microstructure, without bringing about any damage to the surfaces of the electronic parts.
Further, according to the present invention, chip substrates are arranged in a manner such that portions of the chip substrates on which electrodes are to be formed will become light irradiation portions, an electroless plating is conducted on the irradiated portions so as to form electrodes thereon. In this way, by improving the method of arranging the chip substrates, it is possible to form U-shaped terminal electrodes on the chip substrates, thereby rendering the process to become extremely simple.
While preferred embodiments of the invention have been disclosed, various modes of carrying out the principles disclosed herein are contemplated as being within the scope of the following claims. Therefore, it is understood that the scope of the invention is not to be limited except as otherwise set forth in the claims.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.